Capacitor and semiconductor device including the same

ABSTRACT

Provided are a capacitor and a semiconductor device including the capacitor. The capacitor includes a first electrode; a plurality of dielectric films on the first electrode in a sequential series, the plurality of dielectric layers having different conductances from each other; and a second electrode on the plurality of dielectric films, wherein the capacitor has a capacitance which converges to a capacitance of one of the plurality of dielectric films.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2020-0142528, filed on Oct. 29,2020, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The present disclosure relates to capacitors and semiconductor devices.

2. Description of Related Art

The available space occupied by capacitors in integrated circuit devicesis also decreasing with the down-scaling of integrated circuit devices.The capacitor includes upper and lower electrodes and a dielectric filmbetween the upper and lower electrodes, and a dielectric material havinga high dielectric constant is used to exhibit high capacitance. Aleakage current may also flow in the capacitor. There is a need todevelop a technique for minimizing the decrease in capacitance whilereducing a leakage current flowing in the capacitor.

SUMMARY

Provided are capacitors having high leakage current blockingcharacteristics and high capacitance.

Provided are semiconductor devices including a capacitor having highleakage current blocking characteristics and high capacitance.

However, the problem to be solved is not limited to the abovedisclosure.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to an embodiment, a capacitor includes: a first electrode; aplurality of dielectric films on the first electrode in a sequentialseries, the plurality of dielectric layers having different conductancesfrom each other; and a second electrode on the plurality of dielectricfilms, wherein the capacitor has a capacitance which converges to acapacitance of one of the plurality of dielectric films.

The capacitance of the capacitor may converge to a capacitance of adielectric film having the smallest conductance among the plurality ofdielectric films.

Also, a difference in capacitance between the capacitance of thecapacitor and the capacitance of a dielectric film having the smallestconductance among the plurality of dielectric films may be less than adifference in capacitance between the capacitance of the capacitor andthe capacitances of at least one of a remainder of the dielectric films.

A dielectric constant of the dielectric film having the smallestconductance among the plurality of dielectric films is greater than thedielectric constant of at least one of a remainder remaining dielectricfilms.

Also, the dielectric constant of the dielectric film having the smallestconductance among the plurality dielectric films may be 30 or more.

Among the plurality of dielectric films, a dielectric film having thesmallest conductance may include at least one of a perovskite structure,a ferroelectric material, a paraelectric material, or anantiferroelectric material.

Also, the capacitance of the capacitor may be greater 10% or more thanthe capacitance of the dielectric film having the smallest conductanceamong the plurality of dielectric films.

Also, a thickness of a dielectric film having the smallest conductance,among the plurality of dielectrics, has a greater effect on thecapacitance of the capacitor than a thickness of a dielectric filmhaving the largest conductance among the plurality of dielectric films.

A thickness of a dielectric film having the smallest conductance amongthe plurality of dielectric films may be 4 nm or less.

Also, a thickness of a dielectric film having a largest conductanceamong the plurality of films may be 2 nm or less.

The thickness of the capacitor may be 5 nm or less.

Also, a difference in conductance between two of the plurality ofdielectric films may be 10 times or more.

A difference in conductance between a dielectric film having a largestconductance and a dielectric film having a smallest conductance, amongthe plurality of dielectric films, is 100 times or more.

Also, the capacitor may further include a first insertion film, whereinthe plurality of wherein the plurality of dielectric films include afirst, second, and third dielectric film, and the first insertion filmis between the second and the third dielectric films.

The second and the third dielectric films may directly contact the firstinsertion film.

Also, a thickness of the first insertion film may be less than twice athickness of an atomic layer included in the first insertion film.

The second and the third dielectric films may include the same material.

Also, the first and second dielectric films may be in direct contact andmay include different materials from each other.

The capacitor may further include a second insertion film between thefirst and the second dielectric films.

According to an embodiment, a semiconductor device may include atransistor and a capacitor, as described above, electrically connectedto the transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view of a capacitor according to someembodiments;

FIG. 2 shows an equivalent circuit of the capacitor of FIG. 1 accordingto some embodiments;

FIG. 3 is a graph showing a result of measuring capacitance according toa thickness of a dielectric film according to some embodiments;

FIG. 4 is a graph showing a result of calculating an equivalent oxidethickness (EOT) according to a thickness change of a first dielectricfilm having a large conductance according to some embodiments;

FIG. 5 shows a result of calculating a ratio of a dielectric constant ofa capacitor with respect to a dielectric constant of a third dielectricfilm having the smallest conductance from the results of FIG. 4;

FIG. 6 is a diagram illustrating a capacitor including a plurality ofinsertion films according to some embodiments;

FIG. 7 is a diagram illustrating a capacitor including an interface filmaccording to some embodiments;

FIG. 8 is a diagram illustrating a capacitor including four unitdielectric films according to some embodiments;

FIG. 9 is a diagram illustrating a capacitor including two dielectricfilms according to some embodiments;

FIG. 10 is a diagram illustrating a capacitor without an insertion filmaccording to some embodiments; and

FIG. 11 is a cross-sectional view of a semiconductor device according tosome embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to some example embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to like elements throughout, and sizes ofelements may be exaggerated for clarity and convenience of explanation.The example embodiments of the inventive concepts are capable of variousmodifications and may be embodied in many different forms. In thisregard, the present embodiments may have different forms and should notbe construed as being limited to the descriptions set forth herein.Accordingly, the example embodiments are merely described below, byreferring to the figures, to explain aspects. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

Although the terms “first,” “second,” “third,” etc., may be used hereinto describe various elements, components, regions, layers, and/orsections, these elements, components, regions, layers, and/or sections,should not be limited by these terms. These terms are only used todistinguish one element, component, region, layer, or section, fromanother region, layer, or section. Thus, a first element, component,region, layer, or section, discussed below may be termed a secondelement, component, region, layer, or section, without departing fromthe scope of this disclosure.

When the terms “about” or “substantially” are used in this specificationin connection with a numerical value, it is intended that the associatednumerical value includes a manufacturing tolerance (e.g., ±10%) aroundthe stated numerical value. Further, regardless of whether numericalvalues or shapes are modified as “about” or “substantially,” it will beunderstood that these values and shapes should be construed as includinga manufacturing or operational tolerance (e.g., ±10%) around the statednumerical values or shapes.

It will be understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation inaddition to the orientation depicted in the figures. For example, if thedevice in the figures is turned over, elements described as “lower,”other elements or features would then be oriented “above” the otherelements or features. For example, the device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. It will be understoodthat when an element or layer is referred to as being “on” or “above”another element or layer, the element or layer may be directly onanother element or layer or intervening elements or layers.

The singular forms are intended to include the plural forms as well,unless the context clearly indicates otherwise. It should be understoodthat, when a part “comprises” or “includes” an element in thespecification, unless otherwise defined, other elements are not excludedfrom the part and the part may further include other elements.

FIG. 1 is a cross-sectional view of a capacitor 100 according to someembodiments.

Referring to FIG. 1, a capacitor 100 includes a first electrode 110 anda second electrode 120 that are separated from each other, and adielectric layer 130 between the first electrode 110 and the secondelectrode 120. The first electrode 110, the dielectric layer 130, andthe second electrode 120 may be sequentially arranged. For example, oneof the first electrode 110 and/or the second electrode 120 may be alower electrode of the capacitor 100, and the other may be an upperelectrode of the capacitor 100. The dielectric layer 130 may includefirst to third dielectric films 132, 134, and 136 that are sequentiallyarranged. Each of the first to third dielectric films 132, 134, and 136may also include a plurality of sub dielectric films.

The first electrode 110 and the second electrode 120 may includeconductive material. For example, the conductive material may compriseat least one of a metal, a metal nitride, a metal oxide, and/or acombination thereof. For example, at least one of the first electrode110 and the second electrode 120 may include TiN, MoN, CoN, TaN, W, Ru,RuO₂, SrRuO₃, Ir, IrO₂, Pt, PtO, SrRuO₃(SRO), (Ba, Sr)RuO₃ (BSRO),CaRuO₃ (CRO), (La, Sr)CoO₃ (LSCO), and/or a combination thereof.

The physical properties of the first to third dielectric films 132, 134,and 136 may be different from each other. For example, the first tothird dielectric films 132, 134, and 136 may have conductance andcapacitance characteristics different from each other. In someembodiments, at least two of the first to third dielectric films 132,134, and 136 may include materials different from each other. Forexample, the first dielectric film 132 and the second dielectric film134 may include materials different from each other, and the seconddielectric film 134 may include the same material as the thirddielectric film 136, but the present embodiment is not limited thereto.In some embodiments, the first to third dielectric films 132, 134, and136 may include the same material, but may have physical propertiesdifferent from each other. For example, if the first to third dielectricfilms 132, 134, and 136 include the same material, physical properties(for example, conductance, capacitance, etc.) may vary depending on thecrystal structure.

At least one of the first to third dielectric films 132, 134, and 136may include a material having a high dielectric constant. For example,the material may be a high-k dielectric, and/or may have a dielectricconstant greater than silicon dioxide. At least one of the first tothird dielectric films 132, 134, and 136 may use a metal oxide includingat least one metal selected from Ca, Sr, Ba, Sc, Y, La, Ti, Hf, Zr, Nb,Ta, Ce, Pr, Nd, Gd, Dy, Yb, and/or Lu. For example, at least one of thefirst to third dielectric films 132, 134, and 136 may include at leastone of HfO₂, ZrO₂, CeO₂, La₂O₃, Ta₂O₃, and/or TiO₂.

At least one of the first to third dielectric films 132, 134, and 136may include a ferroelectric material, a paraelectric material, and/or anantiferroelectric material. In an example, at least one of the first tothird dielectric films 132, 134, and 136 may include a dielectricmaterial having a non-perovskite structure and/or a perovskitestructure. In some embodiments, one of the first to third dielectricfilms 132, 134, and 136 may include a non-perovskite structure, andanother of the first to third dielectric films 132, 134, and 136 mayinclude a perovskite structure. The dielectric material having anon-perovskite structure may include a metal oxide layer including ametal, such as hafnium (Hf), zirconium (Zr), niobium (Nb), and/oraluminum (Al). As an example, the dielectric material having aperovskite structure may include a dielectric material having an ABO₃series structure. In ABO₃, ‘A’ may be, for example, strontium (Sr),barium (Ba), bismuth (Bi) and/or lanthanum (La); and ‘B’ may be, forexample, titanium (Ti), tantalum (Ta), ruthenium (Ru), hafnium (Hf),zirconium (Zr), and/or molybdenum (Mo).

The capacitor 100 may further include an insertion film 142 in thedielectric layer 130. The insertion film 142 may include a dielectricmaterial having a dielectric constant lower than that of the first tothird dielectric films 132, 134, and 136, and/or may have a very smallthickness. Thus, the insertion film 142 may not operate as a constituentlayer of the capacitor 100. For example, the insertion film 142 may havea thickness less film twice the thickness of the atomic layer of thematerial included in the insertion film 142. For example, the insertionfilm 142 may be a single layer and/or twice an atomic layer.Alternatively, the insertion film 142 may be 7 Å or less.

The insertion film 142 may be an oxide. For example, the insertion film142 may include Al₂O₃, but is not limited thereto.

The insertion film 142 may block a leakage current between the adjacentdielectric films (e.g., the second and third dielectric film 134 and136) and may induce the change of physical properties of the adjacentdielectric films (e.g., the second and third dielectric film 134 and136). For example, when the insertion film 142 is arranged between thesecond dielectric film 134 and the third dielectric film 136, theinsertion film 142 may induce a change in the physical properties. Forexample, the insertion film 142 may affect the crystal structure inand/or induce a crystallinity change of the second dielectric film 134.Thus, even if the second dielectric film 134 and the third dielectricfilm 136 include the same material, because the third dielectric film136 is stacked on the second electrode 120 and the second dielectricfilm 134 is stacked on the insertion film 142, the physical properties(for example, capacitance and/or conductance) may vary. Thus, the use ofthe insertion film 142 may allow the second and third dielectric films134 and 136 to include the same material, thereby facilitating themanufacture of the capacitor 100.

The thickness of the capacitor 100 may be the same as the separationdistance between the first electrode 110 and the second electrode 120.As the degree of integration of an integrated circuit device includingthe capacitor 100 increases, a space occupied by the capacitor 100decreases. The thickness of the capacitor 100 according to someembodiments may be about 5 nm or less. Alternatively, the thickness ofthe capacitor 100 may be about 5 nm or less.

As the thickness of the capacitor 100 decreases, the dielectric layer130 may have conductance due to a leakage current. Thus, the capacitanceof the capacitor 100 may be affected not only by the capacitances of thefirst to third dielectric films 132, 134, and 136; but also theconductance.

FIG. 2 shows an equivalent circuit of the capacitor 100 of FIG. 1according to some embodiments.

A resistor-capacitor (RC) circuit on the left side shown in FIG. 2represents the capacitor 100, and each RC circuit on the rightrepresents the first to third dielectric films 132, 134, and 136,respectively.

For the equivalent circuit of FIG. 2, the total capacitance Cp may beexpressed by the following Equation 1.

$\begin{matrix}{C_{p} = \frac{\begin{matrix}{{{C_{1}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}\left( {G_{3}^{2} + {\omega^{2}C_{3}^{3}}} \right)} + {C_{2}\left( {G_{1}^{2} + {\omega^{2}C_{1}^{2}}} \right)}} \\{\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right) + {{C_{3}\left( {G_{1}^{2} + {\omega^{2}C_{1}^{2}}} \right)}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}}\end{matrix}}{\begin{matrix}\begin{matrix}\begin{matrix}{{\left( {G_{1}^{2} + {\omega^{2}C_{1}^{2}}} \right)\left\lbrack {\left( {G_{2} + G_{3}} \right)^{2} + {\omega^{2}\left( {C_{2} + C_{3}} \right)}^{2}} \right\rbrack} +} \\{{\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)\left\lbrack {\left( {G_{1} + G_{3}} \right)^{2} + {\omega^{2}\left( {C_{1} + C_{3}} \right)}^{2}} \right\rbrack} +}\end{matrix} \\{{\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)\left\lbrack {\left( {G_{1} + G_{2}} \right)^{2} + {\omega^{2}\left( {C_{1} + C_{2}} \right)}^{2}} \right\rbrack} -}\end{matrix} \\\begin{matrix}{{\left( {G_{1}^{2} + {\omega^{2}C_{1}^{2}}} \right)\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)} - \left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)} \\{\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right) - {\left( {G_{1}^{2} + {\omega^{2}C_{1}^{2}}} \right)\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)}}\end{matrix}\end{matrix}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Equation 1, ω is the operating angular frequency of the capacitor100; C₁, C₂, and C₃ respectively are the capacitances of the first tothird dielectric films 132, 134, and 136; and G₁, G₂, and G₃respectively are the conductances of the first to third dielectric films132, 134, and 136.

If the conductance G₁ of the first dielectric film 132 is greater thanthe conductances G₂ and G₃ of the second and third dielectric films 134and 136 and the reciprocal of the reactance (ωC₁, ωC₂, ωC₃) of each ofthe first to third dielectric films 132, 134, and 136 (e.g., G₁>>G₂, G₃,ωC₁, ωC₂, ωC₃), the capacitance Cp of the capacitor 100 may be expressedas Equation 2 below. Here, it is preferable that the conductance G₁ ofthe first dielectric film 132 is greater than 10 times or more than theconductances G₂ and G₃ of the second and third dielectric films 134 and136 and the reciprocal of reactance (ωC₁, ωC₂, ωC₃) of the first tothird dielectric films 132, 134, and 136.

$\begin{matrix}{{C_{p} \approx \frac{\begin{matrix}{{G_{1}^{2}\left\lbrack {{C_{2}\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)} + {C_{3}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}} \right\rbrack} +} \\{{C_{1}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)}\end{matrix}}{\begin{matrix}{{G_{1}^{2}\left\lbrack {\left( {G_{2} + G_{3}} \right)^{2} + {\omega^{2}\left( {C_{2} + C_{3}} \right)}^{2}} \right\rbrack} -} \\{\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)}\end{matrix}}} = \frac{G_{1}^{2}\begin{bmatrix}{{C_{2}\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)} +} \\{{C_{3}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)} + {\alpha\;{C_{1}\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)}}}\end{bmatrix}}{G_{1}^{2}\begin{bmatrix}{\left( {G_{2} + G_{3}} \right)^{2} + {\omega^{2}\left( {C_{2} + C_{3}} \right)}^{2} -} \\{\alpha\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Here, since

$\alpha \equiv \frac{\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}{G_{1}^{2}}$

and G₁>>G₂, G₃, ωC₁, ωC₂, ωC₃, then

$\alpha \equiv \frac{\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}{G_{1}^{2}} ⪡ 1.$

The capacitance Cp of the capacitor 100 may be expressed as in Equation3 below.

$\begin{matrix}{C_{p} \approx \frac{{\left( {C_{2} + {\alpha\; C_{1}}} \right)\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)} + {C_{3}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}}{\begin{matrix}{G_{2}^{2} + {2G_{2}G_{3}} + {\left( {1 - \alpha} \right)G_{3}^{2}} + {\omega^{2}C_{2}^{2}} +} \\{{2\omega^{2}C_{2}C_{3}} + {{\omega^{2}\left( {1 - \alpha} \right)}C_{3}^{2}}}\end{matrix}} \approx \frac{{\left( C_{2} \right)\left( {G_{3}^{2} + {\omega^{2}C_{3}^{2}}} \right)} + {C_{3}\left( {G_{2}^{2} + {\omega^{2}C_{2}^{2}}} \right)}}{\left( {G_{2} + G_{3}} \right)^{2} + {\omega^{2}\left( {C_{2} + C_{3}} \right)}^{2}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Also, if the conductance G₂ of the second dielectric film 134 is greaterthan the conductance G₃ of the third dielectric film 136 (e.g., ifG₂>>G₃), as shown in Equation 4 below, the capacitance Cp of thecapacitor 100 converges to the capacitance G₃ of the third dielectricfilm 136 having the smallest conductance. It is preferable that theconductance G₂ of the second dielectric film 134 is 10 times or morethan the conductance G₃ of the third dielectric film 136. That is, theconductance G₂ of the second dielectric film 134 may be 10 times greaterthan the conductance G₃ of the third dielectric film 136, and theconductance G₁ of the first dielectric film 132 may be 100 times greaterthan the conductance G₃ of the third dielectric film 136. However, theabove is merely an example embodiment based on relative conductance G ofthe dielectric films, and that the relative magnitudes of theconductance may vary.

$\begin{matrix}{{C_{p} \approx C_{3}} = {\epsilon_{0}\epsilon_{r}\frac{A}{t_{3}}}} & \left\lbrack {{Equation}\mspace{11mu} 4} \right\rbrack\end{matrix}$

Consequently, when the capacitor 100 is formed by connecting dielectricfilms (e.g., the first, second, and third dielectric films 132, 134, and136) having a large difference in conductance in series, the capacitanceof the capacitor 100 is most affected by the capacitance of thedielectric film having the smallest conductance. For example, adifference in capacitance between the capacitance of the capacitor 100and the capacitance of a dielectric film having the smallest conductance(for example, the third dielectric film 136) may be less than adifference in capacitance between the capacitance of the capacitor 100and the capacitances of the remaining dielectric films (for example thefirst and second dielectric films 132 and 134). Thus, the capacitance ofthe capacitor 100 may be controlled by controlling the capacitance of adielectric film having the smallest conductance (for example, the thirddielectric film 136).

The capacitance of the capacitor 100 is also affected by the dielectricconstant and the thickness of the dielectric film having the smallestconductance (for example the third dielectric film 136). For example,the dielectric constant of the dielectric film having the smallestconductance may affect the capacitance of the capacitor 100 greater thanthe dielectric constant of the remaining dielectric films (for examplethe first and second dielectric films 132 and 134), and the thickness ofthe dielectric film having the smallest conductance may affect thecapacitance of the capacitor 100 greater than the thickness of theremaining dielectric films. In some embodiments, the thickness of thedielectric film having the smallest conductance may be about 4 nm orless. In some embodiments, the thickness of the remaining dielectricfilms (for example each of the first and second dielectric films 132 and134) may be 2 nm or less. Because the remaining dielectric films mayslightly affect the capacitance of the capacitor 100, it may beunnecessary to have a large thickness. Rather, in some embodiments, ifthe thickness is large, it may be difficult to implement a thin filmcapacitor.

In order to increase the capacitance of the capacitor 100, it ispreferable that the dielectric constant of the dielectric film havingthe smallest conductance is greater than the dielectric constant of theremaining dielectric films. For example, the dielectric constant of adielectric film having the smallest conductance may preferably be about30 or more, and the dielectric film having the smallest conductance mayinclude at least one of a dielectric material, a ferroelectric material,a paraelectric material, and/or an antiferroelectric material having aperovskite structure.

The capacitance of the capacitor 100 may be greater than the capacitanceof the dielectric film having the smallest conductance. For example, thecapacitance of the capacitor 100 may be 10% or greater than thecapacitance of the dielectric layer 130 having a small conductance. Thecapacitance of the capacitor 100 may have a dielectric constant of 35 ormore.

In order to confirm whether the capacitance of the capacitor is affectedby not only the capacitance of the dielectric film but also theconductance of the dielectric film, a capacitor in which two dielectricfilms are arranged in series was fabricated, and the capacitance of thecapacitor was measured.

FIG. 3 is a graph showing a result of measuring capacitance according toa thickness of a dielectric film according to some embodiments. A seconddielectric film L₂ having a capacitance of a certain size, and a firstdielectric film L₁, as depicted by (i) in FIG. 3, the capacitance ofwhich slightly varies depending on the thickness, are connected inseries.

If the capacitance of the capacitor is determined by the capacitances ofthe first and second dielectric films L₁, and L₂, the capacitance of thecapacitor 100 may hardly change according to the thickness as shown by(ii) in FIG. 3. However, as shown by the results of actual measurements,it may be confirmed that the capacitance changes according to thethickness of the first dielectric film L₁ as shown by (iii) in FIG. 3.It may be expected that the capacitance of the capacitor may be affectednot only by the capacitance of each of the dielectric films L₁ and L₂but also by the conductance of each of the dielectric films L₁ and L₂.

Also, it may be seen that, when the thickness of the first dielectricfilm L₁ is small (for example when the thickness of the first dielectricfilm L₁ is about 3.5 nm or less) the capacitance of the capacitorincreases more than the theoretically calculated capacitance. It may bealso seen that, even if the thickness of the capacitor 100 is small,there is a boosting effect of the capacitance due to the conductance.

FIG. 4 is a graph showing a result of calculating an equivalent oxidethickness (EOT) according to a thickness change of the first dielectricfilm L₁ having a large conductance, according to some embodiments. Whena capacitor having a thickness of 60 Å was formed with the thirddielectric film L₃ having the smallest conductance, the EOT was about6.7 Å, as shown by (i) of FIG. 4, which may be, without being limited toa particular theory, a result of calculating EOT according to athickness change of the first dielectric film L₁ when the thickness ofthe capacitor 100 is set to 60 Å and the thickness of the thirddielectric film L₃ having the smallest conductance is set to 35 Å.According to the thickness change of the first dielectric film L₁, thethickness of the second dielectric film L₂ also complementarily changes,and the thickness of the third dielectric film L₃ is constant. It may beseen that, even if the thickness of the first dielectric film L₁ ischanged, the EOT is almost constant. It may be seen that the capacitanceof the capacitor is determined by the third dielectric film L₃ having alow conductance.

A result of measuring EOT according to a thickness change of the firstdielectric film L₁ when the thickness of a capacitor is set to 48 Å andthe thickness of the third dielectric film L₃ having the smallestconductance is set to 40 Å is shown by (ii) of FIG. 4. When the resultsrepresented by (i) are compared to the results represented by (ii), itmay be seen that the larger the thickness ratio of the third dielectricfilm L₃ to the thickness of the capacitor, the larger the capacitance.This may denote that a thin-film capacitor may be implemented byconductance.

When a capacitor having a thickness of 45 Å was formed with the thirddielectric film L₃ having the smallest conductance, the EOT was about5.5 Å, as shown by (iii) of FIG. 4, which may be, without being limitedto a particular theory, a result of measuring EOT according to thethickness change of the first dielectric film L₁ when the thickness of acapacitor is set to 60 Å and the thickness of the third dielectric filmL₃ having the smallest conductance is set to 35 Å. A result of measuringEOT according to the thickness change of the first dielectric film L₁when the thickness of a capacitor is set to 48 Å and the thickness ofthe third dielectric film L₃ having the smallest conductance may be setto 40 Å is shown by (iv) of FIG. 4. It may be seen that even if thethickness of the first dielectric film L₁ is changed, the EOT is almostconstant, and that the capacitance of the capacitor is affected by thethird dielectric film L₃ having the smallest conductance. When theresults represented by (iii) are compared to the results represented by(iv), with regard to the thickness of the capacitor, it may be seen thatthe larger the thickness ratio of the third dielectric film L₃, thelarger the capacitance.

FIG. 5 shows a result of calculating a ratio of a dielectric constant ofthe capacitor 100 with respect to a dielectric constant of the thirddielectric film L₃ having the smallest conductance from the results ofFIG. 4. As illustrated in FIG. 5, it may be seen that the dielectricconstant of the capacitor 100 is greater than that of the thirddielectric film L₃. It may be seen that the conductance of thedielectric film induces a boosting effect of the capacitance.

FIG. 6 is a diagram illustrating a capacitor 100 a including a pluralityof insertion films according to some embodiments. A capacitor 100 a ofFIG. 6, compared to the capacitor 100 of FIG. 1, may further include asecond insertion film 144 between the first dielectric film 132 and thesecond dielectric film 134. Like the first insertion film 142, thesecond insertion film 144 may include a low dielectric material, and/ormay have a thickness less than twice the thickness of an atomic layer.In some embodiments, the second insertion film 144 may not act as anoperation layer of the capacitor 100 a. Also, in some embodiments, thesecond insertion film 144 may block a leakage current by changing aninterface between the first dielectric film 132 and the seconddielectric film 134, and/or may affect the crystal structures of thefirst dielectric film 132 and the second dielectric film 134 such thatthe crystal structures are different from each other. For example,direct contact between the second insertion film 144 and at least one ofthe first dielectric film 132 and/or the second dielectric film 134 mayaffect the growth and/or crystallization of the at least one of thefirst dielectric film 132 and/or the second dielectric film 134.

Because the second insertion film 144 may affect the crystal structuresof the first dielectric film 132 and/or the second dielectric film 134,the first dielectric film 132 and the second dielectric film 134 mayinclude the same material but have different physical properties. Thus,even if the first dielectric film 132 and the second dielectric film 134include the same material, the first dielectric film 132 and the seconddielectric film 134 may have physical properties, for example,conductance or capacitance, different from each other.

FIG. 7 is a diagram illustrating a capacitor 100 b including aninterface film according to some embodiments. A capacitor 100 b of FIG.7, compared to the capacitor 100 of FIG. 1, may further include aninterface film 152 between the first electrode 110 and the dielectriclayer 130. The interface film 152 may block and/or reduce a leakagecurrent from flowing between the first electrode 110 and the secondelectrode 120. For example, the interface film 152 may act as a leakagecurrent reduction layer. In some embodiments, the interface film 152 mayinclude Al₂O₃ and/or may be doped with a dopant. The interface film 152may have a thickness of 1 nm or less. Although not shown, the interfacefilm 152 may also be arranged between the dielectric layer 130 and thesecond electrode 120.

FIG. 8 is a diagram illustrating a capacitor 100 c including four unitdielectric films according to some embodiments. A capacitor 100 c ofFIG. 8, when compared to the capacitor 100 of FIG. 1, may furtherinclude a fourth dielectric film 138. The fourth dielectric film 138 mayhave a physical property different from those of the first to thirddielectric films 132, 134, and/or 136. For example, the fourthdielectric 138 may have a different conductance or capacitance from thefirst to third dielectric films 132, 134, and/or 136. In someembodiments, the all of the first to fourth dielectric films 132, 134,136, and 138 may have different physical properties to each other. Whenthe fourth dielectric film 138 is arranged to directly contact the thirddielectric film 136, the fourth dielectric film 138 may include amaterial different from that of the third dielectric film 136, but thepresent embodiment is not limited thereto. Although not shown, aninsertion film may further be arranged between the fourth dielectricfilm 138 and the third dielectric film 136, and the fourth dielectricfilm 138 may include the same material as the third dielectric film 136,but may have different physical properties. The number of dielectricfilms may vary depending on applications.

Additionally, though not illustrated, the capacitor 100 c may furtherinclude one and/or both of the second insertion film 144 and/or theinterface film 152 as depicted in FIGS. 6 and 7, respectively.

FIG. 9 is a diagram illustrating a capacitor 100 d including twodielectric films according to some embodiments. A capacitor 100 d ofFIG. 9, compared to the capacitor 100 of FIG. 1, may include twodielectric films. For example, the capacitor 100 d may include thesecond and third dielectric films 132 and 136, and the insertion film142 may be arranged between the second and third dielectric films 132and 136. The second and third dielectric films 132 and 136 may includethe same material, but may have physical properties different from eachother, for example, because of the insertion film 142. Due to thedifference in conductance according to some embodiments, the capacitanceof a capacitor is converged to the capacitance of a dielectric filmhaving a small conductance, and thus, a unit dielectric film 130 of thecapacitor may be two.

FIG. 10 is a diagram illustrating a capacitor 100 e without an insertionfilm according to some embodiments. A capacitor 100 e of FIG. 10,compared to the capacitor 100 d of FIG. 9, may not include an insertionfilm. In this case, it is preferable that the second dielectric film 134and the third dielectric film 136 include different materials from eachother such that the second dielectric film 134 and the third dielectricfilm 136 have different physical properties. If the unit dielectric film130 includes different materials from each other, the capacitor 100 maynot include an additional insertion film 142, and the number of unitdielectric films 130 may be three or more.

FIG. 11 is a cross-sectional view of a semiconductor device 11 accordingto some embodiments. For brevity of explanation, descriptionssubstantially the same as those given with reference to FIG. 1 will beomitted.

Referring to FIG. 11, the semiconductor device 11 may include asubstrate 1100, a gate structure 1300, an interlayer insulating layer1400, a contact 1500, and a capacitor 100 may be provided. The substrate1100 may include a semiconductor substrate. For example, the substrate1100 may include a silicon substrate, a germanium substrate, or asilicon-germanium substrate. The substrate 1100 may be a channel.

A first source/drain region 1210 and a second source/drain region 1220may be provided in the substrate 1100. The first and second source/drainregions 1210 and 1220 may be separated from each other in a firstdirection DR1 parallel to an upper surface of the substrate 1100. Forexample, the first source/drain region 1210 and the second source/drainregion 1220 may each be on a side of the channel. In some embodiments,the first and second source/drain regions 1210 and 1220 may be formed byimplanting impurities into the substrate 1100.

The gate structure 1300 may be provided on the substrate 1100. The gatestructure 1300 may be provided between the first and second source/drainregions 1210 and 1220 and/or on the channel. The gate structure 1300 mayinclude a gate electrode 1310 and a gate insulating layer 1320. The gateelectrode 1310 may include a conductive material. For example, the gateelectrode 1310 may include a metal or polysilicon.

The gate insulating layer 1320 may be disposed between the gateelectrode 1310 and the substrate 1100. The gate insulating layer 1320may electrically isolate the substrate 1100 from the gate electrode1310. The gate insulating layer 1320 may include a dielectric material.For example, the gate insulating layer 1320 may include a Si oxide(e.g., SiO₂), an Al oxide (e.g., Al₂O₃), or a high dielectric material(e.g., HfO₂). For example, in some embodiments, the gate insulatinglayer 1320 may include an oxide of the substrate 1100.

The interlayer insulating layer 1400 may be provided on the substrate1100 to cover the gate structure 1300. The interlayer insulating layer1400 may include an insulating material. For example, the interlayerinsulating layer 1400 may include a Si oxide (e.g., SiO₂), an Al oxide(e.g., Al₂O₃), and/or a high dielectric material (e.g., HfO₂). In someembodiments, the interlayer insulating layer 1400 may be omitted. Thesubstrate 1100, the first source/drain region 1210, the secondsource/drain region 1220, and the gate structure 1300 may constitute atransistor.

The capacitor 100 may be connected to one of the first source/drainregion 1210 or the second source/drain region 1220, and, in someembodiments provided on the interlayer insulating layer 1400. Thecapacitor 100 is depicted as the capacitor 100 illustrated in FIG. 1,but is not limited thereto, and the capacitors 100 a, 100 c, 100 d, and100 e described above may also be applied. Because the capacitance ofthe capacitor 100 converges to the capacitance of the dielectric filmhaving the smallest conductance, the capacitance characteristic of thecapacitor is improved.

The contact 1500 may be provided between the first electrode 110 and thefirst source/drain region 1210. The contact 1500 may penetrate throughthe interlayer insulating layer 1400. The contact 1500 may electricallyconnect the capacitor 100 and the first source/drain region 1210 to eachother. For example, in some embodiments, the contact 1500 mayelectrically connected the first electrode 110 or the second electrode120 to the first source/drain region 1210. The contact 1500 may includea conductive material (e.g., a metal). Though not illustrated, in thecase wherein the interlayer insulating layer 1400 is not included in thesemiconductor device 11, the capacitor 100 may be directly connected tothe first source/drain region 1210. In this case, the first electrode110 and/or second electrode 120, as depicted in FIG. 1, may act as acontact between the capacitor 100 and the first source/drain region1210.

The present disclosure may provide a capacitor having improved leakagecurrent characteristics and capacitance characteristics.

The present disclosure may also provide a semiconductor device includinga capacitor having improved leakage current characteristics andcapacitance characteristics.

However, the inventive concepts are not limited to the above disclosure.

It should be understood that the example embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope asdefined by the following claims.

What is claimed is:
 1. A capacitor comprising: a first electrode; aplurality of dielectric films on the first electrode in a sequentialseries, the plurality of dielectric films having different conductancesfrom each other; and a second electrode on the plurality of dielectricfilms, wherein the capacitor has a capacitance which converges to acapacitance of one of the plurality of dielectric films.
 2. Thecapacitor of claim 1, wherein the capacitance of the capacitor convergesto a capacitance of a dielectric film having the smallest conductanceamong the plurality of dielectric films.
 3. The capacitor of claim 1,wherein a difference in capacitance between the capacitance of thecapacitor and the capacitance of the dielectric film having the smallestconductance among the plurality of dielectric films is less than adifference in capacitance between the capacitance of the capacitor andthe capacitances of at least one of a remainder of the plurality ofdielectric films.
 4. The capacitor of claim 1, wherein a dielectricconstant of the dielectric film having the smallest conductance amongthe plurality of dielectric films is greater than a dielectric constantof at least one of a remainder of the plurality of dielectric films. 5.The capacitor of claim 1, wherein a dielectric constant of thedielectric film having the smallest conductance among the plurality ofdielectric films is 30 or more.
 6. The capacitor of claim 1, wherein,among the plurality of dielectric films, a dielectric film having thesmallest conductance includes at least one of a perovskite structure, aferroelectric material, a paraelectric material, or an antiferroelectricmaterial.
 7. The capacitor of claim 1, wherein the capacitance of thecapacitor is 10% or greater than the capacitance of the dielectric filmhaving the smallest conductance among the plurality of dielectric films.8. The capacitor of claim 1, wherein a thickness of a dielectric filmhaving the smallest conductance, among the plurality of dielectrics, hasa greater effect on the capacitance of the capacitor than a thickness ofa dielectric film having the largest conductance among the plurality ofdielectric films.
 9. The capacitor of claim 1, wherein a thickness of adielectric film having the smallest conductance among the plurality ofdielectric films is 4 nm or less.
 10. The capacitor of claim 1, whereina thickness of a dielectric film having the largest conductance amongthe plurality of dielectric films is 2 nm or less.
 11. The capacitor ofclaim 1, wherein a thickness of the capacitor is 5 nm or less.
 12. Thecapacitor of claim 1, wherein a difference in conductance between two ofthe plurality of dielectric films is 10 times or more.
 13. The capacitorof claim 1, wherein a difference in conductance between a dielectricfilm having a largest conductance and a dielectric film having asmallest conductance, among the plurality of dielectric films, is 100times or more.
 14. The capacitor of claim 1, further comprising: a firstinsertion film, wherein the plurality of dielectric films include afirst, second, and third dielectric film, and the first insertion filmis between the second and the third dielectric film.
 15. The capacitorof claim 14, wherein the second and the third dielectric films directlycontact the first insertion film.
 16. The capacitor of claim 14, whereina thickness of the first insertion film is less than twice a thicknessof an atomic layer included in the first insertion film.
 17. Thecapacitor of claim 14, wherein the second and the third dielectric filmscomprise the same material.
 18. The capacitor of claim 14, wherein thefirst and the second dielectric films are in direct contact and includedifferent materials from each other.
 19. The capacitor of claim 14,further comprising: a second insertion film between the first and thesecond dielectric films.
 20. A semiconductor device comprising: atransistor; and the capacitor according to claim 1 electricallyconnected to the transistor.